Apple Shake 4 - Manual (Page 681)

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Keying
Shake provides powerful, industry-standard keying tools
in the Primatte and Keylight nodes, along with additional
keying nodes such as LumaKey and SpillSuppress. When
combined with Shake’s other filtering, masking, and
color-correction nodes, you have detailed control over
every aspect of the keying process.
About Keying and Spill Suppression
The first part of this chapter presents different strategies for pulling keys in Shake.
Keying can be loosely defined as the creation of a new alpha channel based upon the
pixel color (a pure blue pixel, for example), luminance (a very dark pixel), or Z depth (a
pixel 300 Z units away, for example) in an image. Keying is discussed as a separate
process from masking, which can be loosely defined as the creation of an alpha
channel by hand through the use of painting, rotoshapes, or imported alpha masks
from 2D or 3D renders in other software packages. For more information on these
masking techniques, see Chapter 19, “
Using Masks .”
If you are not familiar with Primatte and Keylight (Shake’s primary bundled keyers), you
are encouraged to work through the keying lessons in the Shake 4 Tutorials book prior
to reading through this chapter.
32-bit Support in Primatte and Keylight
As of Shake 4, the Primatte and Keylight nodes preserve 32-bit image data.